The communication distance of wireless module is an important index. How to maximize the effective communication distance zui has always been a problem for customers. Based on the debugging experience, this paper makes some instructions on the selection and use of the antenna, hoping to help engineers quickly debug the communication distance.
The primary parameter that affects the communication distance of the wireless module is the transmitting power. The transmitting power of the wireless module and the corresponding ideal transmission distance can be found in the manual.
First is the selection of the antenna:
The main indicators of the antenna include the following: frequency range, SWR or VSWR standing wave ratio, antenna gain, polarization mode and impedance. Frequency range as needed; Standing wave is less than 1.5 than zui; The antenna gain also affects the transmission distance. The polarization modes are divided into linear polarization and circular polarization. The impedance needs to match the output impedance of the wireless module, generally 50 ohms. Pay special attention to the VSWR parameters here. After you buy the antenna, use the zui network analyzer to test SWR.
The comparison table of standing-wave ratio, return loss and transmitted power is shown in table 1.
As can be seen from the above table, when VSWR=1.5, the theoretical transmitted power is 96%; when VSWR=2, the transmitted power is only 88.9%; some antenna VSWR index is less than 2; when the zui antenna is selected, the VSWR is less than 1.5, which can obtain higher transmitted power.
Secondly, the directivity of the antenna:
Antennas all have directivity, which means that antennas have different radiation or receiving ability to different directions in space. The directivity of an antenna is usually measured by a pattern. Figure 1 shows the pattern of an antenna with a frequency range from 2400MHz to 2500MHz.
When the antenna is placed vertically, the direction of the deep red zui is the direction of the antenna radiation or the strong receiving capacity of zui. Therefore, when installing the antenna, you should install the antenna in the direction pointing to the red as far as possible, so as to ensure good enough signal quality. In addition, the metal plate has a shielding effect on the signal, so there should be no metal plane in the direction of transmission and reception.
There are also some antennas in the manual given the antenna direction diagram is represented by two-dimensional diagram, divided into h-plane and e-plane, as shown in figure 2.
When testing the communication between wireless modules, the antenna's directivity must be taken into account. When the communication space has no shielding and the antenna direction corresponds to the strong zui radiation direction, the communication distance can reach to the large zui. If the antenna is not installed properly, the communication distance will become short, or even unable to communicate.
Engineers in testing wireless module communication, often weak signal, communication distance does not meet the instructions in the manual or high packet loss rate, in determining the wireless module itself under the condition of no problem, please test the performance of the antenna itself, and then to test according to the direction of antenna radiation is strong, can get better test results.
AW516x is a series of nano-type zigbee wireless modules with low power consumption and high cost performance developed by guangzhou zhiyuan electronics based on NXP JN516x wireless microcontroller, and provides a complete application integration scheme based on IEEE802.15.4 standard ISM frequency band.
Products after a series of radio frequency instrument testing and certification, and combined with many years of market experience and the actual needs of the industry users, to integrate the wireless products extremely complicated communication protocol to the built-in MCU, change numerous for brief, greatly simplify the complex wireless products development process, make your product at a lower cost to market quickly, because the small size and low power design, is widely used in various kinds of intelligent equipment.